Laser diode manufacturers typically offer a line of laser diodes that are designed to operate at different output powers. Sometimes these different laser diodes are structurally the same, but are simply operated at different bias levels to achieve the different output powers. Generally, the manufacturers package laser diodes in different ways that depend on the applications for which they are to be used. For example, a high power (e.g., 10 mw) laser diode designed for analog applications such as CATV systems, which must meet relatively stringent specifications for linearity, are often housed in a standard in-line hermetic package such as a butterfly package that includes internal cooling to maintain the temperature of the laser diode. In CATV applications, such high power lasers are often used in the forward transmission path from the headend to the network node that is in communication with the cable subscriber. Other lower power (e.g., 2 mw) laser diodes, which do not need to meet such stringent specifications for linearity, are often housed in a low cost TO-style coaxial can that does not provide internal cooling.
FIG. 1 shows an example of a coaxial can laser package that is incorporated into a laser module that includes a lens, an optical fiber for receiving the light from the laser package. In particular, coaxial can laser package 120 includes a laser diode chip 101 that is fixed to a stem 103 via a heat sink 102. A cap 104 hermetically seals the package 120. The cap 104 has a window 109 through which light from the laser diode chip 101 is emitted. The can laser package 120 is depicted in operative association with a lens holder 106. Lens holder 106 includes a lens 105 and an optical fiber 107. An optical isolator 110 is incorporated into the pigtail of the laser package 120 to maintain optimum distortion and noise performance. As previously noted, the coaxial can laser package 120 does not include a cooling element nor a mechanism for monitoring the temperature of the laser diode chip 101.
As might be expected, lower power, uncooled laser packages such as the aforementioned coaxial can laser package are typically substantially less expensive than an internally cooled butterfly laser package. Accordingly, it would be desirable to employ a coaxial can laser so that it can operate at higher optical powers while meeting the more stringent specifications for linearity that are often required of such lasers, while also provisioning the can laser package with a cooling and temperature monitoring arrangement, all at a cost that is less than a commercially available high power butterfly laser package.